The riddle of didymo

NIWA scientists continue their research into didymo, hoping to find out more about the conditions most suited to its establishment.

Didymo – the invasive freshwater alga also known as 'rock snot' – is running rampant in some South Island rivers but seems not to grow in others, especially spring-fed systems. Scientists suspect that the spring-fed rivers may lack some particular nutrient that didymo requires. And the fact that didymo blooms in low-nutrient rivers sets it apart from most other algal blooms, which are usually triggered by high nutrient levels.

NIWA scientists are working on didymo in collaboration with Environment Canada, and with additional funding from the Department of Conservation, Fish & Game NZ, and Meridian Energy.

"At this stage, we're working out how to identify rivers and streams that are susceptible and those that are resistant to didymo growth," says NIWA scientist Dr Cathy Kilroy. "We're looking in detail at water chemistry, to tease out what micro-nutrients didymo may like and which ones may be present or absent in different waters.

"While the research is unlikely to lead to control methods for didymo, it could potentially enable us to predict where it will and won't grow."

Contact: Dr Cathy Kilroy